'sar' issue or core dump issue?

[Lizhang Qin]

Hi,

I am experience some performance issue for user space app, when
looking at 'sar' result, it showed things like below.

		          CPU     %user     %nice   %system   %iowait    %steal     %idle
	08:30:02          all      3.29      0.00      9.16      0.01
0.00     87.54
	08:30:12          all      0.38      0.00      2.40      0.38
0.00     96.84
	08:43:39          all      0.28      0.00      1.17      0.87
0.00     97.68

It shows all the records between 08:30:12 to 08:43:39 are missing.
Does it mean kernel actually lose all the statistic data during that
period?  How could that happen though?

I notice there is a big core dump file were written for a crash app
running in the machine.
Could a core dump interfere all the kernel scheduling on all cores (I
have 4 physical CPU adn 8 virtual cores).

Thanks.
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